The present invention relates to a rubber composition and a tire prepared using the rubber composition.
In recent years, while vehicles have higher performances and more powerful engines, a concern over safety is increasing and a demand for enhanced grip performance of a tire is also increasing. For example, various performances when the vehicles are running at a high speed are required.
Grip performance depends on a hysteresis loss characteristics of a rubber composition. For enhancing grip performance of a rubber composition, a method of increasing amounts of styrene and vinyl in a styrene-butadiene rubber (SBR) and raising a glass transition point is known. However, in this case, the grip performance under low temperature as well as abrasion resistance are reduced, and there is a risk of causing brittle fracture. Another method of improving grip performance by compounding a large amount of oil is also known, however, in such a case, the rubber composition thus prepared possesses deteriorated abrasion resistance due to decrease in destruction resistance property.
A method of using a low molecular weight SBR is also known. However, in such a case, since the low molecular weight SBR still has crosslinkable double bonds, a part of the low molecular weight components forms crosslinking with the matrix rubber and is taken in the matrix and thereby there is a problem that an adequate level of hysteresis loss cannot be obtained.
Furthermore, in JP2000-319447A, a method of using a powder of a specific inorganic compound such as tungsten in a rubber composition is disclosed. Similarly, in JP2002-80642A, a method of using an acrylic resin such as polyacrylic ester particles in a rubber composition is disclosed. However, both of the rubber compositions thus prepared still have a room for further improvement in grip performance.
Further, there is known a rubber composition for a tread comprising polyurethane (urethane particle) in order to improve wet grip performance, abrasion resistance and heat build-up property while maintaining dry grip performance (cf. JP2002-97303A). The polyurethane described in JP2002-97303A comprises a hard segment comprising urethane bonds and a soft segment comprising polyether or polyester. Strength is needed for a rubber composition for a tire comprising a diene rubber. In order to enhance strength of a rubber composition for a tire, further improvements are still required for thermoplastic polyurethane.
An object of the present invention is to provide a rubber composition being capable of enhancing grip performance and abrasion resistance. Another object of the present invention is to provide a tire using the rubber composition.